Typical examples of a device which can suction-adhere to a vertical or inclined surface and move along it are those disclosed in the specification and drawings each of U.S. Pat. Nos. 4,095,378, 4,926,957 and 4,934,475.
Such a device has a pressure receiver, a partitioning means mounted on the pressure receiver and defining a pressure reduction space in cooperation with the pressure receiver and a surface, and a pressure reducing means for discharging a fluid from the pressure reduction space to decrease the pressure inside the pressure reduction space. The partitioning means is constructed such that its part to be contacted with the surface is displaceable by a relatively small force toward and away from the surface.
FIG. 5-C of U.S. Pat. No. 4,926,957 discloses a partitioning means of a structure comprising a lip portion allowed to extend along a surface, an extension further extending obliquely from a front end of the lip portion in a direction away from the surface, and an inside connecting portion and an outside connecting portion connecting the inner peripheral edge portion of the lip portion to a pressure receiver, the lip portion, extension and both connecting portions being integrally formed a flexible material such as synthetic rubber. In such a partitioning means, the lip portion is brought into contact with the surface, and it is moved toward and away from the surface by the elastic deformation of the inside connecting portion and the outside connecting portion. If a bulge such as a weld line is present on the surface, the extension and the lip portion ride over the bulge under the guiding action of the extension. Thus, the partitioning means can pass over the bulge smoothly and move, without posing a problem such as the inward folding of the lip portion.
The above-mentioned partitioning means of a structure including a lip portion allowed to extend along a surface has been demonstrated to surpass a partitioning means of other structures in terms of various properties including the bulge-passing properties. However, the conventional partitioning means including a lip portion which is allowed to extend along a surface includes problems to be solved. For instance, if the surface to which the device is caused to suction-adhere is a curved surface having a relatively small radius of curvature, there is a tendency that the lip portion of the partitioning means is not bent along the curved surface owing to the rigidity possessed by the lip portion, and thus the lip portion is gradually separated from the surface, beginning with its outer peripheral edge portion. If such a tendency is augmented, the inner peripheral edge portion of the lip portion is also released from the surface. As a result, the pressure reduction space may become open, destroying the suction-adhesion of the device to the surface.